Selective ethylation of the cellulose molecule

ABSTRACT

This invention relates to a process for the selective ethylation of cellulosic fibers. More particularly, this invention relates to a process for the selective ethylation of cellulosic fibers and a subsequent crosslinking of said fabrics to produce fabrics with improved crease recovery and abrasion resistance.

United States Patent Roberts May 2, 1972 SELECTIVE ETHYLATION OF THE CELLULOSE MOLECULE John G. Roberts, Cheadle Hulme, England Assignee: The United States of America as represented by the Secretary of Agriculture Inventor:

Filed: Sept. 4, 1970 Appl. No.: 69,865

U.S. CI ..8/1l6.3, 8/120, 260/232 Int. Cl. ..D06m 15/58, D06m l l/O4, D06m 13/02 Field of Search ..8/1 16.3, 120

References Cited OTHER PUBLICATIONS Primary Examiner-Donald Levy Assistant ExaminerJ. Cannon Attorney-R. Hoffman and W. Bier [5 7] ABSTRACT This invention relates to a process for the selective ethylation of celluiosic fibers. More particularly, this invention relates to a process for the selective ethylation of celluiosic fibers and a subsequent crosslinking of said fabrics to produce fabrics with improved crease recovery and abrasion resistance.

1 Claims, 1 Drawing Figure PATENT-EM? 2 m2 6 FIRST EXPERIMENT X SECOND EXPERIMENT NUMBER OF TREATME N TS INVENTOR JOH N G. ROBERTS ATTORNEY SELECTIVE ETHYLATION OF THE CELLULOSE MOLECULE A non-exclusive irrevocable, royalty free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

Previously, work on alkylation of cellulosic fabrics has resulted in non-selective alkylation of the reactive hydroxyl groups on the elementary fibrils of the cellulose. However, it has been found that this non-selective alkylation is not always desirable, particularly if the fabrics are subsequently to be treated with a crosslinking agent. This is because the efficacy of the crosslinking agent being to some extent dependent on the location of available reactive hydroxyl groups.

Cotton fabrics when crosslinked to improve their crease recovery properties suffer from losses in strength and in resistance to abrasion. This is particularly true when the cellulosic fabric has been alkylated prior to crosslinking.

According to the present invention, a process has been found for the selective ethylation of cellulosic fabric followed by a crosslinking treatment to produce fabrics with improved crease recovery and abrasion resistance. These unexpected results were obtained only with ethylated cellulose.

The differences between the behavior of the methylated and the ethylated fabrics are at first sight surprising. The important differences between the two series of samples lie in the markedly different distribution of the methyl and ethyl groups and the associated differences in accessibility. These must influence the sites involved in subsequent cross-linking and it is believed that these differences of location of crosslinks are responsible for the improved balance of properties. The observed distribution of ethyl (Table 4) and of methyl substituents (Table 5) shows that ethylation involves fewer anhydroglucose units which are substituted to a higher degree than occurs in the methylation series. This suggests that under the conditions of the ethylation reaction the most easily accessible regions are reacted first. This would leave only the hydroxyl groups in the less accessible regions available for crosslinking and it is feasible that at the particular level of substitution when the easily accessible region is more or less fully substituted that these hydroxyl groups would be the only ones available for crosslinking. Thus there would be an uneven distribution of both crosslinks and ethyl substituents with a preponderance of the latter in the most accessible areas in the cotton fibers. It is these areas which would suffer most abrasion damage and the ethyl substituents act in two ways, increasing abrasion resistance by plasticizing or lubricating and by blocking hydroxyl groups and so reducing the level of crosslinking. These are likely factors which would influence resistance to abrasion damage in the manner observed.

In the preferred process of the instant invention, cellulosic fabric is treated in 2 N-aqueous sodium hydroxide solution for 20 minutes at room temperature on a laboratory jig. The excess solution is allowed to drain from the batched fabric. The fabric is then treated in a mixture of diethyl sulfate and toluene for 30 minutes at 80 C. on the same jig. The fabric is then washed free of the treating mixture and dried. The cellulosic fabric is then crosslinked using dimethylolethyleneurea as a crosslinking agent and magnesium chloride as a catalyst.

When cellulose was methylated instead of ethylated prior to crosslinking the results were not the same. The treated fabrics did not show improved crease recovery nor abrasion resistance.

The following examples illustrate but do not limit the scope of this invention. Any suitable dialkyl sulphate may be used in place of diethyl sulphate and any suitable crosslinking agent may he used in place ofdimethylolethyleneurea. For example, dimethylpropyleneurea may be used. All percentages in the examples are by weight.

EXAMPLE 1 Cotton fabrics were ethylated in a series of repeated treatments. The fabrics were pretreated in 2 N-sodium hydroxide then reacted with a solution consisting of 200 ml of diethyl sulphate and 200 ml of toluene for 30 minutes at 80 C. The fabrics were then washed free from the treating mixture with methylated spirits followed by hot water containing a wetting agent. Table 1 shows the properties of ethylated cotton fabrics.

EXAMPLE 2 Ethylated cotton fabrics prepared as in Example 1 were crosslinked with a 4 percent aqueous solution of dimethylolethyleneurea containing magnesium chloride as a catalyst. The fabrics with a pickup of about 80 percent were dried and cured at 165 C. for 3% minutes. Physical properties of the crosslinked ethylated cotton are shown in Table 2.

The process was repeated a second time and results are shown in Table 3.

EXAMPLE 3 Ethylated cotton fabrics prepared as in Example 1 were crosslinked with a 8 percent aqueous solution of dimethylolethyleneurea containing magnesium chloride as a catalyst. The fabrics with a pickup of about 80 percent were dried and cured at 165 C. for 3% minutes. Physical properties of the crosslinked ethylated cotton are shown in Table 2.

The process was repeated a second time and results are shown in Table 3.

EXAMPLE 4 Ethylated cotton fabrics prepared as in Example 1 were crosslinked with a 12 percent aqueous solution of dimethylolethyleneurea containing magnesium chloride as a catalyst. The fabrics with a pickup of about 80 percent were dried and cured at 165 C. for 3% minutes. Physical properties of the crosslinked ethylated cotton are shown in Table 2.

The process was repeated a second time and results are shown in Table 3.

The FIGURE in the accompanying drawing shows the extent of reaction produced by repeated ethylation of cotton fabric with diethylsulfate at 80 C. after pretreatment with 2N NaOH.

TABLE 1 Properties of Ethylated Cotton Fabrics Acid hydrolysis Number of Ethoxyl Moisture Rapidly Rate of ethylation D.S. regain hydrolyzed hydrolysis of treatments fraction residue (sec") TABLE 2 [Physical properties of crosslinked ethylated cotton] Single Treated Crease recovery thread with angle (degree) tensile Extension Abrasion Ethyl DMEU strength at break resistance D.S. (percent) Dry W (t: (percent) (rubs) 0 0 7O 64 288 8. 7 1, 405 O 4 111 210 7.2 70 0 8 116 103 ll. 7 0 12 131) 121 145 6.1 0.05.. 0 65 76 285 8. 0 1, 805 70 0.05 l 112 110 205 0.7 1,015 0.05 8 l3tl 120 ltil 0.0 405 0.05 11! l-l'J 11!! I51 5. K 350 (1.24 0 70 x7 :13 x. It, 205 0.2-1 10'.) Ill ill-'1 7. .5 1,035 0.24 .s 1313 \2': m5 1;, s 1170 (LLB-l l'. 1251': 127 lfill ti. 3 (Hi5 0.31 U TI 7B '15.: 8. l -l, 8135 75 0.3L. 1 ms 217 we 7. 2 2, 5% 0.3L 12-1 111 Hill 11.3 1,310 0.31. 1.! 1'30 113 173 ll. l l, l-lll TABLE 3 We claim: [Physical properties of crosslinked cthylated cotton] 1. A process for producing cellulosic fabrics with improved singk crease recovery and abrasion resistance which process comth 1 thmald E t Ab pnsesz 311% egree tens" X a. treati cellul si f bric in a 2 N-a ueous s dium Ethyl DMEU Strength at break resistance a o c a q o D.S. Dry w (g) (per nt) (rubs) hydroxide solution, l I

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